Aromatic hydrocarbons and aliphatic hydroxy compounds are routinely nitrated to form nitroaromatics and aliphatic nitrates using a mixed sulfuric/nitric nitration acid. Examples of the nitration products are trinitrotoluene, dinitrotoluene, nitrobenzene, nitroglycerin, butyl nitrate, amyl nitrate, hexyl nitrate, octylnitrate and the like. Nitration acids used in the nitration contain at least 65 weight percent H.sub.2 SO.sub.4 and about 1-20 weight percent HNO.sub.3. For example, a mixed acid containing 20 weight percent HNO.sub.3 and 68 weight percent H.sub.2 SO.sub.4 is a very effective nitration acid. When desired even higher H.sub.2 SO.sub.4 concentrations can be used including mixtures of oleum and nitric acid. Such nitration processes are well-known.
All of the nitration processes result in a spent nitration acid containing the initial H.sub.2 SO.sub.4 and water and additional water formed in the nitration. The spent acid also contains residual nitric acid and usually small amounts of nitrous acid. Because of the nitrogen acid contamination, the spent acid presents a severe disposal problem. If these contaminants are removed there are numerous commercial uses for the resulting sulfuric acid.